// static
double FieldTrial::HashClientId(const std::string& client_id,
const std::string& trial_name)
{
// SHA-1 is designed to produce a uniformly random spread in its output space,
// even for nearly-identical inputs, so it helps massage whatever client_id
// and trial_name we get into something with a uniform distribution, which
// is desirable so that we don't skew any part of the 0-100% spectrum.
std::string input(client_id + trial_name);
unsigned char sha1_hash[SHA1_LENGTH];
SHA1HashBytes(reinterpret_cast<const unsigned char*>(input.c_str()),
input.size(), sha1_hash);
COMPILE_ASSERT(sizeof(uint64)<sizeof(sha1_hash), need_more_data);
uint64* bits = reinterpret_cast<uint64*>(&sha1_hash[0]);
return BitsToOpenEndedUnitInterval(*bits);
}
double RandDouble()
{
return BitsToOpenEndedUnitInterval(RandUint64());
}
